Rotary Axis: Angular Output and Unwinding

Rotary work covers rings, tumblers, pens, tool handles and anything else where the tool works on a cylindrical surface rather than a flat sheet. CamDRAW handles it by treating the surface as an unrolled sheet and converting the coordinates on output.

The profile decides

Rotary machining is not a switch inside an operation. It comes from the postprocessor, so it is selected through the profile.

Open the Profile section, the topmost of the four in the CamDRAW docker, and choose a profile holding a rotary preset. The rest of the docker adapts automatically, because the fields required are defined by the preset.

Keeping a flat preset in one profile and a rotary one in another is the practical way to run both on the same machine. Switching is then one dropdown selection rather than a reconfiguration.

The workpiece fields change

With a rotary profile active, the Workpiece section shows different inputs.

Length is the length of the cylindrical part along its axis.

Circumference is the distance around it. A checkbox in front of the field lets you enter a diameter instead, if that is the measurement you have.

The CorelDRAW page then represents the unrolled surface: you lay out artwork on the full circumference as though it were a flat sheet, and CamDRAW converts it on output.

Z zero point

Two options, and which is correct depends on how your machine is set up.

Cylinder surface puts the Z origin on the outside of the part.

Cylinder axis puts it on the centre line of the rotary axis.

Machines whose rotary axis is fixed and known usually work from the axis. Setting the zero on the surface each time suits a machine where the part diameter changes between jobs.

Outside or inside

Machining above the cylinder axis is normal outside work: engraving or cutting the outer surface.

Machining below the cylinder axis is inside work, where the tool reaches into the bore. This is what internal ring engraving needs, and it is a specific setting rather than something that happens automatically.

Rotation and mapping

Two ways of writing the output, set in the postprocessor per axis.

Rotation converts the length dimension along that axis into angular coordinates, based on the workpiece radius. The control receives degrees.

Mapping, sometimes called unwinding, keeps the value as a length rather than converting it, for controls that expect the mapping themselves, such as Y to A.

Which you need depends entirely on your controller. If the part comes out stretched or compressed around the circumference, this is the setting to check.

Which axis rotates

The rotary axis can be either the CorelDRAW X or Y axis, set in the postprocessor. Machines differ in how the rotary is mounted, so this is a configuration point rather than a fixed rule.

For the same reason, the circumference and diameter inputs can be swapped between the two axes in the postprocessor settings.

A direction factor of 1 or -1 reverses the direction of rotation, which is the setting to change when the engraving comes out mirrored around the part.

Checking the result

The 3D view in the NC program section renders rotary programs as they will run, with the geometry wrapped around the part rather than flat. Cutting moves are blue and rapid moves red.

This is worth more on rotary work than on flat, because an error in the axis configuration is difficult to picture from the code and obvious in the rendering.

Getting the configuration right

Rotary setups vary more between machines than flat ones do. Axis assignment, direction, mapping and the Z zero convention all depend on the machine and the control.

If the geometry is correct but the output does not behave, the postprocessor is where it is adjusted. Our support team helps with adapting a preset to a specific rotary setup.